What is aprs.fi?

This is a global APRS database, which archives position tracking,
weather and message information collected from the
APRS-IS
network. Position data and routes traveled by APRS tracking stations are shown on an interactive map
which can be zoomed and panned easily. New and updated data is shown
on the map in real time without need to reload or refresh the page!
Tracking data is stored in the database for six months.

You can also use this service to find
your QTH/QRA locator
(or your grid square) by simply pointing at a location on the map. Entering
a QTH locator in the search box will move the map to the given location and
show a rectangle containing the given locator. Short and extended locators
are supported (from KP20 to KP20LE20TP).

About APRS:

This page shows real-time information collected from the
Automatic Position Reporting System Internet network (APRS-IS). APRS is used by
amateur (ham) radio operators
to transmit real-time position information, weather data, telemetry and messages over
the radio. A vehicle equipped with a
GPS receiver,
a VHF transmitter or
HFtransceiver
and a small computer device called a tracker transmits it's location,
speed and course in a small data packet, which is then
received by a nearby iGate receiving site which forwards the packet on the Internet.
Systems connected to the Internet can send information
on the APRS-IS without a radio transmitter, or collect and display
information transmitted anywhere in the world.